High-throughput communication methods have been studied and developed, whose transmission efficiency is increased through control of a modulation scheme and coding rate in a downlink of high-speed mobile communication in accordance with radio propagation path conditions of the downlink between a wireless base station and wireless mobile station. Further, still higher-throughput communication methods have been studied and developed, in which modulation and code scheme (hereinafter referred to as “MCS”) is changed for each subcarrier in accordance with radio propagation path conditions.
FIG. 20 is a diagram showing a configuration of conventional modulation information. Since, in a method of adaptively modulating each subcarrier depending on radio propagation path conditions, modulation and code scheme is periodically changed for each subcarrier, a base station must notify a mobile station of modulation information such as changed modulation and code scheme for each subcarrier. Modulation information is often in a form of mapping of a combination of the modulation scheme and coding rate as shown in FIG. 21. An information amount of several bits is assigned to each subcarrier and modulation information in which modulation and code schemes of all subcarriers are described (Multilevel Information: hereinafter referred to as MLI) is transmitted from the base station side to the mobile station side together with data. In the downlink, as shown in FIG. 22A, a frame consisting of a pilot subframe, MLI subframe, and data subframe is transmitted. The mobile station analyzes the MLI to check modulation and code scheme of each subcarrier before performing demodulation/decoding. In an uplink from the mobile station to the base station, as shown in FIG. 22B, a frame consisting of a received SIR subframe and data subframe is transmitted.
In Japanese Patent Laid-Open No. 2003-169036, as shown in FIG. 23, a group of blocks (a group of subcarrier groups), each consisting of several subcarriers, is formed in accordance with received power values of a plurality of subcarriers, modulation and code scheme is determined for each block, and a subcarrier number at a specific position in each block (subcarrier number at the head position or that of the rear position of a block) and the determined modulation scheme and coding rate are notified.    Patent Document 1: Japanese Patent Laid-Open No. 2003-169036